My 2.8 has a very strange idle problem that I am having trouble figuring out. When i start it in the morning it will idle around (give or take) 2000, which might be because of the cold start valve. I don't know how high the cold start valve is supposed to bring it, so I cant know for sure. When am driving and the engine speed is up around 3000 and come to a light, i put in in neutral (4-speed manual) and it will stay at the speed it was at while i was driving and then slowly start to fall, or it will stay at 3000, or anywhere between 3000 and 2000. The part that has me puzzled is that it seems to prefer either 2000, 2500, or 3000. With this kind of consistent inconsistency , it makes me think it's the ECM trying to figure something out, but failing. If the engine speeds does fall, it will fall a little bit (about 500RPM) then stay and fall again. Everything seems to be happening in increments of 500.
Hopefully I haven't confused you as well. What do you think?
Don't worry about the cold start, it only fires while the starter is cranking unless it's stuck open.
Does sound like you have a vac leak. As a test pull the air duct from the cleaner. Start the engine and place your finger over the iac port while it's running. If you have leaks it will keep running. If you don't... well it should die.
You might also take your IAC out and clean it with some carb cleaner.
[This message has been edited by Dodgerunner (edited 09-25-2007).]
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09:55 PM
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
My my motor continues to run after plugging the IAC port. So, how do i locate the exact spot of a vacuum leak. Rodneys' stainless kit is very tempting, but I would rather fix this problem without spending 118 buxx. i KNOW FOR SURE that i have a vacuum leak on the charcoal canister and possibly the EGR. Dang, maybe I should just get those hoses. I haven't checked the EGR tube yet, it may have a hole in it.
I'd start by capping off all the ports that are not needed to run the engine. You probably only need the map line functioning to run.
A common leak can be the brake booster line or a split in the rubber coupler that bridges between the IAC pipe under the TB and connects to where the cold start inj. is.
One other trick is to spray water on the vac fittings to see if it changes the idle.
Also wiggle the lines to see if they are not spit under the intake.
Also wiggle your EGR pipe. They break off at one end or the other from rust and vibration or make sure the EGR valve is not stuck open. Does it move if you press up on the diaphram.
[This message has been edited by Dodgerunner (edited 09-25-2007).]
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10:16 PM
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
My EGR is new so it damn well better work, and i'm sure it does. What is the charcoal canister for? I also found a slightly larger than most black hose that stuck directly into the TB and went out under the manifold so I cant tell where it's headed. It is really loose.
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11:04 PM
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
The black pipe in the bottom right of the photo is where the air goes from the IAC port. There should be a small o-ring inside the throttle body hole that seals the pipe into the throttle body. The other end goes down to the intake manifold. If any part of that leaks it will cause a high idle.
EDIT: I just saw your 2nd post and yes it goes into that hole. Make sure the o-ring is in that hole too.
[This message has been edited by Hudini (edited 09-25-2007).]
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11:11 PM
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
i need a grommet then, huh? the end of the pipe that attaches into the manifold is secure with a big rubber thing. It surprises me that such a high idle can caused by that. Can all that extra air really squeeze through the tiny opening and cause it to idle so high?
Look inside the hole on the throttle body where the black pipe connects and see if the o-ring is intact. Also wiggle the black pipe to make sure the rubber hose is tight. Another member had a high idle for years before tracing it to the metal pipe under the rubber hose. It had become loose over the years. It does not take much air to cause a high idle.
Here is what the black pipe looks like with everything out of the way.
I do have the o-ring, so i still have my money on a vacuum leak. I will be taking my manifold off in the next couple of days to do some other work, and i'll fix the vacuum leak then. I checked out my EGR tube; looks good. If you have any other ideas, please tell
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11:57 PM
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
how much wiggle should that rubber connector have? Mine wiggles in every direction and up and down. Look at my pic, it will wiggle to every obstruction in my pic. is that too much? duh, i'm sure it is.
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11:59 PM
Sep 26th, 2007
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
Well it is apparent to me that i need to replace the rubber thing. But "rubber thing" isn't gonna find me a part on a search engine, so what is the official name of that piece? Idle air control tube?
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12:02 AM
MordacP Member
Posts: 1300 From: Clovis, California, US Registered: Sep 2007
It's just a short piece of rubber hose. Nothing special. Buy a foot of it and cut to length. Not sure of the exact size so you probably need to take the black metal pipe with you.
[This message has been edited by Hudini (edited 09-26-2007).]